Heat treatment of rails



I Patented Feb. I, 1933 PATENT OFFICE JOHN BRUNNEB, Oi CHICAGO, ILLINOIS mum TREATMENT or RAILS No Drawing.

This invention relates to metallurgy and more particularly to the heat treatment of metals and alloys to improve the qualities thereof and still more particularly to the heat treatment of steel rails.

This invention is substantially an improvement of the invention set forth in my U. S. Patent No. 1,277,372 issued September 3, 1918.

The process of U. S. Patent No. 1,277,372 substantially comprises a method of heat treating steel rails to obtain therein a more uniform and fine grain structure and a better surface than had heretofore been obtainable. The method substantially comprises rollin the rail to a section larger than the desired nished section; cooling the rail to temperatures below the thermal critical range; reheating the rail to temperatures above the thermal critical temperatures (approximately 800 0.); rolling the rail to the desired finished section; and slowly cooling the rail to room temperatures. This method produced a finished rail having a fine grain structure which imparted thereto great toughness. The rail .product, however, did not possess sufficient surface hardness to make it resistant to severe service conditions.

One of the objects of the present invention 0 is to increase the surface hardness of the rail product of my prior invention.

Another object of the present invention is to provide heat-treating methods whereby the surface hardness of a steel rail may be materially increased at its ends where the greatest abrasion and battering takes place in service under the rolling loads of motive power and transportation equipment.

Another object of the present invention 0 is to provide a steel rail having an interior of relatively high ductility throughout the entire length of the rail and an exterior of relatively high hardness at the ends of the rail.

Another object. of the present invention is to improve and facilitate the manufacture of steel rails.

Other objects and advantages will be apparent as the invention is more fully disclosed.

Application med October 22, 1981. Serial No. 570,496.

In accordance with the objects of the present invention I have found that I may impart a relatively high surface hardness to the relatively tough fine grain structure in the rail prepared in accordance with the invention of my prior patent, thereby materially increasing the resistance of the railto service conditions, by subjecting the rail to certain heatstreating methods. The heattreating methods substantially comprise the following steps 2 At the conclusion of the final rolling operation the finished rail is cooled to temperatures approximating 300 (1, and is then reheated to relatively uniform temperatures which are slightly above the thermo-critical range of the specific composition of steel used therein and then cooling the head of the rail at and near its ends in a quenching medium until the surface temperature of this part of the rail has been lowered at least partially through the blue-heat range (approximately 288 vC. to 316 C.) but to temperatures not lower than 200 C. {thereafter the rail is allowed to slowly cool to atmospheric temperatures.

In this manner I first effect a refinement of the internal grain structure of the rail, increasing its uniformity and toughness, and then a hardening of the surface of the head thereof at and near its ends, thereby obtain ing a desired amount of external surface hardness of the rail ends to resist abrasion and battering of the rail ends in the track in service.

As a specific embodiment of the practice of this invention I will disclose the method as applied to a steel rail composition comprising carbon .40/, 85%; manganese .40/1.60%; phosphorus, not over .08% sulphur, not over .08%; silicon, not over 1.50%, depending on the section of rail used and the intended service of the treated rail.

In accordance with the teaching of my prior patent a billet of steel in the above noted composition is heated to temperatures above the thermal critical range and rolled into a section approximating but larger than the desired finished rail section and then is cooled to temperatures below the thermal critical range. Preferably but not necessarily the per cent reduction in area remaining is only that which is sufficient to obtain an accurate section of the rail.

The cooled rail is then reheated to relatively uniform vtemperatures approximating 800 C. and is thereafter rolled to the desired finished section. The finished rail is thereafter allowed to cool to an average temperature of not less than 300 C. and is again reheated to relatively uniform temperatures approximating 800 G., and from these temperatures is quenched on the head at and near both ends of the rail until the surface temperatures of this part of the rail has been lowered partially through the blue-heat range but not lower than 200 C. The quenched rail is then allowed to cool slowly to atmospheric temperatures.

The rail product thus produced will be found to have retained the fine grain structure of my prior patent with an exterior surface on top of the head at the end of the rail of greater hardness than heretofore obtainable by cold working means alone. For example, the finished rail product of my prior patent will have a surface hardness of approximately 250-280, as measured on the Brinell scale. The finished rail product of the specific embodiment of the present invention will have a surface hardness of the head at and near the ends of the rail approximating from 340 to 410, depending on the section and intended service of the heat treated rail.

The exact cooling temperatures and the time intervals of cooling may be widely varied depending upon the composition of the steel, the finished hardness desired, and upon the1 internal grain structure desired in the ra1 While I have disclosed as a specific embodiment the steps of rolling the rail to a section larger than the desired finished section, cooling to below and then reheating to above the thermal critical range, and then rolling to the desired finished section, I may omit this particular sequence of steps and roll the rail directly down to the desired finished section if desired. The rail thus prepared may be cooled to temperatures below the thermal critical range, but above 300 (3., reheated to temperatures approximating but above the thermal critical range, and thereafter quenched and otherwise treated as in the three specific embodiments described.

Whereas, also the above invention has been disclosed with particularity asregards to its application to a specific rail composition, it is apparent that with modifications in the steel composition, modifications in the heat treating process may be made accordingly. Such modifications and departures are contemplated as may fall within the scope of the following claims.

What I claim is:

1. The method of heat treating steel rails to increase the surface hardness thereof on the head at and near its ends which comprises heating the rail to temperatures approximating but above the thermal critical range, quenching the head of the rail at and near its ends until the surface temperatures of the head at its ends approximate but are not less than 200 C. the center portion of the rail intermediate the said ends being substantially not chilled and thereafter slowly cooling the rail to atmospheric temperatures.

2. The method of hardening the surface of steel rails having an approximate composition of carbon .40/.85%; manganese .40/1.60%; phosphorus, not over .08%; sulphur, not over .08%; silicon, not over 1.50%; which comprises heating the rail to temperatures approximating but above the thermal critical range, quenching the head of the rail at and near its ends until the surface temperatures of the head at and near its ends approximate but are not less than 200 C. the center portion of the rail intermediate said ends being substantially not chilled and thereafter slowly cooling the rail to room temperatures.

3. The method of hardening the surface of steel rails having an approximate composition of carbon .40/85%; manganese .40/1.60%; phosphorus, not over 08%; sulphur, not over 08%; silicon, not over 1.50%; which comprises heating the rail to temperatures approximating 800 C., quenching the head of the rail at and near its ends until the surface temperatures of the head at and near its ends approximate but are not less than 200 C. the center portion of the rail intermediate the ends being substantially not chilled and thereafter slowly cooling the rail to room temperatures.

4. The method of hardening the surface of steel rails having an approximate composition of carbon .40/.85%; manganese .40/1.60%; phosphorus, not over 08%; sulphur, not over 08%; silicon, not over 1.50% which comprises heating the rail to temperatures approximating 800 C., quenching the head of the rail at and near. its ends in water until the surface temperatures of the head at and near its ends approximate but are not less than 200 0., the center portion of the rail intermediate the ends being substantially not chilled and thereafter slowly cooling the rail to room temperatures.

5. The method of forming steel rails which comprises heating the rail ingot or billet to rolling temperatures above the thermal critical range, rolling to a section larger than the desired finished rail section, cooling to I not over 08%; sulphur,

finished section, cooling to temperatures below the thermal critical range but above 300 (1, reheating to temperatures approximating but above the thermal critical range, quenching the head of the rail at and near its ends until the surface temperatures of the head at and near its ends lie within the blue heat range but above about 200 C. the center portion of the rail intermediate the ends being substantially not chilled, thereafter cooling the rail slowly to room temperatures.

6. The method of forming steel rails having an approximate composition of carbon .40/.85% manganese .40/1.60% phosphorus,

not over 08%; silicon, not over 1.50%; which comprises heating the rail ingot or billet to rolling temperatures above the thermal critical range, rolling to a section larger than the desired finished section, cooling to temperatures lower than the thermal critical range, but above about 300 (1, reheating to temperatures approximating but above thermal critical range, rolling to the desi j 'j finished section, cooling to temperatures below, the thermal critical range but above about 300 0., reheating to temperatures approximating but above the thermal critical range, quenching the head of the rail at and near its ends until the surface temperatures of the head at and near its ends lie within the blue-heat range but above 200 C. the center portion of the rail intermediate the ends being substantially not chilled and thereafter slowly cooling the rail to atmospheric temperatures.

7. The method of forming steel rails which ing temperatures above the thermal critical range, rolling the rail to the desired finished section, cooling the rail to temperatures below the thermal critical range but above about 300 C., reheating the rail to temperatures approximating but above the thermal critical range, quenching the head of the rail at and near its ends until the surface temperatures of the head at its ends approximate but are above 200 C., the center portion of the rail intermediate the ends being substantially not chilled, and thereafter cooling the rail slowly to room temperatures.

8. The method of forming steel rails from a rail ingot or billet having a composition of carbon .40/.85%; manganese .40/1.60% phosphorus, not over 08%; sulphur, not over 08%; silicon, not over 1.50%; which comprises heating the rail ingot or billet to rolling temperatures above the thermal critical range, rolling the rail to the desired finished section, cooling the rail to temperatures below the thermal critical range but above about 300 (3., reheating to temperatures approximating but above the thermal critical range, quenching the head of the rail at and near its ends until the surface temperatures of the head comprises heating a rail ingot or billet to rollat and near its ends approximate but are above 200 C. the center portion of the rail intermediate the ends being substantially not chilled, thereafter slowly cooling the rail to atmospheric temperatures.

9. The method of treating an elongated steel article to render the end sections thereof harder than the middle section, which comprises heating the said article to temperatures above the critical temperature and then quenching said end sections to a temperature approximating but not less than 200 C. the center portion thereof intermediate the ends being substantially not chilled and thereafter slowly cooling the entire article to room temperatures.

10. The method of treating steel rails to harden the same which comprises quenching the head of the rail at and near its ends from a temperature above the critical temperature to a temperature approximating but not less than 200 C. the center portion thereof intermediate said ends being not substantially chilled and thereafter slowly cooling the rail to room temperatures.

In witness whereof, I have hereunto signed my name. J OHN BRUNNER. 

